In conventional diaphragm pumps for pumping viscous liquids such as paint, the first component to fail is frequently the diaphragm. In addition to the excessive wear imposed upon the diaphragm by being flexed to extremes usually in the range of 1725-2000 times per minute, one factor leading to premature failures in diaphragms is uneven localized stress concentrations created upon assembly of the pump. In one type of these pumps, the upper and lower pump housing portions which clamp and hold the annular periphery of the plastic diaphragm each define four or five mutually facing, cooperative, concentric, and annular gripping ridges. When a new diaphragm is to be installed, it is placed into position between the upper and lower housings and their mutually cooperating ridges. The housings are clamped tightly together with the ridges biting into, deforming and tightly clamping and sealing the corresponding annular periphery of the diaphragm. As the plastic of the diaphragm flows into the valleys between the ridges, the overall plastic flow is generally uncontrolled. That is, plastic flow radially inwardly from the innermost annular ridge may be greater at some areas than others. This often results in ripples and distortion in the inner portion of the diaphragm which results in uneven stress concentrations. Coupled with the high frequency reciprocal flexing, excessive stress concentrations localize at specific points in these areas, which results in premature failure. Adding to this structural debility is the imperfect manner in which the diaphragm is centered relative to the ridges and the corresponding pumping chambers within which the diaphragm reciprocates. For each increment of misalignment from a perfectly centered position, there is a correspondingly greater risk of resulting localized stress concentrations in the mounted diaphragm, and consequently, of premature failure.
Other problems commonly associated with diaphragm pumps of this type include complex disassembly for servicing and cleaning and difficulty in fine tuning the pump components for maximum performance and efficiency.
What is needed is a diaphragm pump which helps to prevent uneven stress concentrations in the diaphragm and which is easier to assemble, repair and operate.